1. Field of the Invention
The present invention relates to a device for transferring the position of an angled abutment from a model to an implant installed in the jawbone of a patient.
2. Description of the Related Art
A dental restoration, such as a prosthetic bridge, may be attached to an edentulous jaw by means of implants. Four implants may be used to fix a single dental restoration either in the upper or the lower jaw. Using only four implants, two posterior and two anterior implants, in the edentulous jaw can take the benefit of tilting the two posterior implants up to a maximum of approximately 45 degrees relative a longitudinal axis of the anterior implants. The anterior implants, in turn, are normally positioned with their longitudinal axes parallel to a normal of a surface of the jawbone. Tilting the posterior implants has e.g. the advantage that longer implants may be used and that coronal ends of the tilted implants, to which the dental restoration may be attached, will be further apart compared to using substantially parallel installed implants. Furthermore, it may not be possible to position the posterior implants straight due to anatomical structures, such as nerves located in the jawbone. However, with a tilted implant, penetrating the nerve can be avoided and still provide sufficient space between top surfaces of the implants to e.g. provide for a stable support structure for a dental bridge.
An abutment is used between the implant and the dental restoration e.g. to properly seat the dental restoration to the implant. For a tilted posterior implant, an angled abutment can be used whereas a straight or a slightly angled abutment can be used for an anterior implant. The angled abutments for the tilted posterior implants can be angled 30 degrees relative a longitudinal axis of the implant. If an angled abutment is used for the anterior implant, the abutment can be angled 17 degrees relative the longitudinal axis of the anterior implant.
Each of the implant and the abutment can have anti-rotational features, which are also referred to as indexing means. The indexing means may e.g. comprise a multi-sided interface, such as a hexagonal interface. The indexing means provides a fixed rotational relationship between the implant and the abutment. If indexing means is used, the abutment is connected to the implant in a stepwise rotational relationship. Thus, the rotational position of the abutment relative the implant is set by the indexing means. The rotational position can be manually adjusted to provide a desired rotationally relationship or orientation between the implant and the abutment.
Using conventional surgery, such as flap surgery, the four implants are installed in the jawbone of a patient. The implants are tightened using e.g. a torque wrench to a predetermined value, such as 35-45 Ncm. Then, an abutment is attached to each implant. After suturing, an impression coping may be attached to the abutment. An impression using e.g. silicon soft putty material may be taken for transferring the position of the abutment to a stone model. The impression includes the rotational position relative the jawbone, and thus relative the installed implants, of the angled abutments installed on the posterior implants. Then, the dental restoration can be fabricated based on the stone model with installed implant replicas and abutments. To provide a proper fit between connection members of the dental restoration and the abutments, the rotational position of the angled abutments relative the jawbone/model is used when the dental restoration is fabricated. For straight abutments, the rotational position is not an issue.
A surgical template may be used to install implants substantially vertical or slightly tilted relative the surgical template. The position of the implants can be preplanned using a CAD (Computer Aided Design) procedure, such as the Procera® system provided by Nobel Biocare®. The surgical template as well as the dental restoration may be prefabricated based on data from the CAD procedure prior to installing the implants in the jawbone. When a surgical template is used during surgery, the implant is installed to a predetermined depth. When the implants are installed substantially vertical or slightly tilted relative the surgical template, straight abutments may be used. Hence, the rotational position of the straight abutment relative the implant is not an issue.
It has been proposed to use a surgical template also for installing implants tilted up to approximately 45 degrees. Hence, angled abutments will be required. It has also been proposed to manufacture a dental restoration, which requires angled abutments, prior to installing the implants. Thus, the surgical template and the dental restoration can be provided at the same time and the dental restoration installed as soon as the implants have been installed. However, a prefabricated dental restoration presumes a predetermined rotational position of the angled abutments relative the jawbone and thus the tilted implants. When a surgical template is used, the dental restoration has not been based on the position of the implants as installed in the jawbone of the patient, as in the case of conventional surgery. Hence, any angled abutment has to be positioned relative the implant to fit the rotational position presumed when the dental restoration was manufactured. This can be cumbersome. For angled abutments, there may be a conflict between the depth of the implant in the jawbone and the rotational position of the angled abutment on the implant. It is difficult, if not impossible, to control the rotational position of the angled abutment relative the jaw bone/installed implant such that it fits the prefabricated dental restoration. It may be difficult e.g. if the abutment has to be tightened to the implant before the dental restoration is tightened to the angled abutment. If the implant and the abutment have indexing means, correct rotational positioning of the angled abutment becomes even more cumbersome, as the depth of the implant in the jaw bone and the rotational position of the indexing means of the implant would have to be controlled at the same time. In some situations, it may even be impossible to provide a proper fit between the angled abutment and the dental restoration. For example, the indexing means of the angled abutment and the indexing means of the tilted implant may not mate at the rotational position desired.